What is Longitudinal Centre of Floatation(COF)?

This is at the geometric centre of the ship’s water plane area and is the point about which the ship will trim.

Consider the ship where a weight is shifted longitudinally.


It can be seen that the LCF is in the same position in the ship’s length as the point where the initial and final waterlines intersect.

It may be helpful to think of the ship as a child’s see-saw that has its pivot point situated at the LCF.


Because the water plane area changes shape and size with draught the position of the LCF will also change with draught.


The position of the LCF is normally quoted in hydrostatic data as being so many metres forward of the after perpendicular.

The position of the LCF is important because if a ship experiences a change of trim, some of that change of trim must be applied to the aft draught and the remainder applied to the forward draught as can be seen.


In this case: Aft draught increases; Forward draught decreases.